Non-Aqueous Electrolyte and Secondary Battery Containing the Same

Abstract

Disclosed is a non-aqueous electrolyte containing a non-aqueous solvent, a solute dissolved in the non-aqueous solvent, and a hydrogenated terphenyl. The solute comprises an alkali salt containing boron and an alkali salt containing no boron. An amount of the hydrogenated terphenyl contained in the non-aqueous electrolyte is preferably 0.5 mass % to 3.5 mass %. For example, LiBF4, NaBF4 or KBF4 is used as the alkali salt containing boron, while LiPF6, LiClO4, LiAsF6, LiCF3SO3, LiN(SO2CF3)2, LiN(SO2C2F5)2 or LiC(SO2CF3)3 is used as the alkali salt containing no boron.

Description

TECHNICAL FIELD [0001] The present invention relates to a non-aqueous electrolyte excellent in reliability and a secondary battery containing the same. Specifically, the present invention relates to a non-aqueous electrolyte that provides a non-aqueous electrolyte secondary battery excellent in cycle life characteristics and also excellent in safety during overcharge. BACKGROUND ART [0002] As overcharge of a non-aqueous electrolyte secondary battery proceeds, an excessive amount of lithium is released from a positive electrode, causing degradation in thermal stability of the positive electrode. A negative electrode absorbs the lithium released from the positive electrode. However, when the positive electrode releases the lithium excessively, the lithium deposits on the surface of the negative electrode. In this case, thermal stability of the negative electrode as well as the positive electrode is remarkably degraded. Eventually, the battery generates heat, and the safety is degraded...

AI Technical Summary

Benefits of technology

[0019] A hydrogenated terphenyl included in a non-aqueous electrolyte oxidatively polymerizes during overcharge of a battery. As a result, the internal resistance of the battery is increased, and the battery is protected. The oxidative polymerization potential of the terphenyl is increased due to partial hydrogenation (adding hydrogen). This inhibits oxidative polymerization reaction in the battery during storage at high temperatures or during charge / discharge cycles. Accordingly, it is possible to ensure high-temperature storage characteristics or charge / discharge cycle characteristics, and safety during overcharge at the same time.

[0020] The high-temperature storage characteristics or the charge / discharge cycle characteristics and the safety during overcharge can be further improved by allowing diphenyl ether to be included in the non-aqueous electrolyte.

[0021] Further, an alkali salt containing boron has an effect of inhibiting oxidative polymerization of the hydrogenated terphenyl and diphenyl ether during storage at high temperatures or during charge / discharge cycles of the battery.

[0022] In view of the above, according to the present invention, it is possible to provide a non-aqueous electrolyte secondary battery excellent in high-temperature storage characteristics or charge / discharge cycle characteristics, and excellent in safety during overcharge.

Problems solved by technology

As overcharge of a non-aqueous electrolyte secondary battery proceeds, an excessive amount of lithium is released from a positive electrode, causing degradation in thermal stability of the positive electrode.

However, when the positive electrode releases the lithium excessively, the lithium deposits on the surface of the negative electrode.

Eventually, the battery generates heat, and the safety is degraded.

Accordingly, there may be a possibility that the internal pressure of the battery rises greatly, and leakage occurs in normal use of the battery.

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